In a landing gear of an aircraft, a shock absorber is provided to absorb and dissipate energy upon impact of the landing. Such a shock absorber typically comprises an outer tube and an inner tube, or a cylinder and a piston. A fluid chamber is formed between the two members to accommodate a fluid that acts as a shock absorber fluid spring. A fluid may be a liquid and/or gas. In order to seal the fluid chamber, the shock absorber is provided with a seal between the two members.
For example, UK patent application publication No. GB2482414 discloses an aircraft shock absorber that comprises an outer tube and an inner tube. This publication discloses use of a primary seal and a spare seal arranged in series between two tubes along the common longitudinal axis, and at least one bypass line that can be closed by means of a switching valve. The bypass line connects the fluid-filled chamber and a space that is located between the seals. When the primary seal leaks, the pressure is removed from the primary seal by closing the switching valve provided in the bypass line, and the spare seal takes over the sealing function. The switching valve used in this shock absorber has a complicated structure including a valve sleeve, a valve slide, an anti-turn device and an actuating pin.
It is therefore desirable to provide a reliable seal assembly for an aircraft shock absorber with a simpler structure.